Background info and Clearing up Misconceptions- from AIMS book, Energy Explorations: Sound, Light, and Heat
Jessica Forgety
Sound is a form of energy. Any form of energy can be changed from its form into another form of energy. Examples of energy are: light, heat, sound, electrical, mechanical, and chemical.
Sound travels. The speed at which it travels changes based on the present conditions. For example, during a lightning storm, sound travels at one mile per five seconds. That is fast!
Sound is produced by vibrations. A vibration is something that moves back and forth. In the case of sound, it is waves which are moved back and forth. “If you could see them, they would look like ripples that spread out when a pebble is dropped in a pond.”
Humans can hear vibrations at a certain range of speed per second, from 20 to 20,000 vibrations per second. Animals can hear sound that has higher vibration than 20,000 per second!
“The vibrating material may be a solid, liquid, or gas.” Typical sounds we hear are vibrations that travel through air. “Sound waves travel much faster through solids and liquids than through gases because the molecules of solids and liquids are closer together.”
“The pitch of the sound can be varied by changing the rate of vibration.” A pitch can be high or low. Pitch is based on the frequency of vibration.
Volume is the based on the amount of vibration traveling through a gas, solid, or liquid.
AIMS Education Foundation (2010). Energy Explorations: Sound, Light, and Heat. Fresno, California: Aims Education Foundation.
Jamie
Text Book
Back ground info and clearing up misconceptions- from Science in elementary education methods, concepts, and inquiries book Jamie Szczygiel
Sound is produced by mechanical radiation, or the movement of energy from one place to another through a medium such as air or water (sound cannot be produced in a vacuum). Vibrations from an object moving back and forth cause molecules in the surrounding medium to begin vibrating and radiating waves of sound energy.
Sounds are vibrations and travel in waves.
Sound is produced by vibrating objects. The pitch of the sound can be varied by changing the rate of vibration.
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of chemicals. Energy is transferred in many ways.
Air is needed in all cases to make vocal cords vibrate. It is difficult to speak while breathing in because the normal way humans make sounds is by breathing out. Molecules and sounds
Sounds are simply waves of compressed molecules pulsating outwards in all directions and planes from a vibrating source.
A sound fades away when energy behind the original vibrations is used in the transmitting process.
Loudness
Intensity or “loudness” is what we actually hear.
Loudness is a matter of individual perception.
Intensity can be consistently and accurately recorded by a sensitive sound detector in terms of decibel, a unit of measurement in sound. The distinction between loudness and intensity may be too subtle for most children.
A boost of energy forces any vibrating medium to vibrate to and fro more widely than usual, but in the same amount of time. It compresses molecules more forcefully, so the greater energy is able to move more molecules.
The farther away we are from the source, the weaker the sound that gets to us. Molecules are pushed less because progressively less energy is available.
Waves
Water is sometimes used as an analogy to teach how sound travels. A pebble is dropped into water, and a circular series of ripples spread out on the water’s surface. Useful to show class but contains two defects.
Water waves are up and down motions that travel at right angles to the line of the waves, known as transverse waves. Sound waves come from back and forth motions that make longitudinal waves.
Water waves move only horizontally, whereas sound waves travel outward in all planes.
The wave idea is useful to distinguish between sounds and noises. A sound consists of regularly pulsating vibrations; the time interval between each compression and rarefaction is the same. Noise is heard when irregular vibrations are passed on.
Forced vibrations
Thomas Edison used his knowledge of forced vibrations when inventing the phonograph. He attached a sharp needle to a thin diaphragm that vibrated when sound waves struck it. The needle was placed against a cylinder wrapped with soft metal foil. As he spoke, he slowly cranked the cylinder around and around. The vibrating needles cut a series of impressions into the metal. To play back his sounds, he places the needle in the impression first scratched and cranked the cylinder. As it followed the impressions, the needle was forced to vibrate, thus causing the diaphragm to vibrate. Edison could hear his voice!
Sympathetic Vibrations
When tuning forks are of identical pitch, sound waves arrive at the proper time to set the still fork in motion. Each air compression pushes a prong as it starts to bend in from a previous one and each rarefaction arrives as the prong starts to bend back out. The steady, timed, push-pause-push rhythm sets the fork vibrating in almost the same way as you would push someone on a swing.
Natural Frequencies
Every solid object has a natural frequency of vibration.
Properties of Objects and Vibrations
Every object has certain physical properties that produce “appropriate” vibrations.
Strange sounds
Oven cooling racks, barbecue grills, and other grid like objects of metal make particularly strange, even eerie, sounds. These sounds come from the overtones produced when the many parts of the object vibrate differently.
Speeds of Sound
Light travels at about 297,000 kilometers (186,000 miles) per second. At sea level and 42 degrees F, sound waves move about 330 meters per second in the air, only as fast as a low-power rifle bullet. Sound also travels in liquids and solids.
It moves about 5 times faster in water than it does in air; in steel, sound may travel 15 times faster than it does in air.
Three conditions affect the speed of sound: density, the elasticity, or “springiness,” of the molecules conducting the sound, and temperature. Density by itself does not increase sound.
Sound and Temperature
Sound travels faster when temperature goes up. (1 ft per second fast in air for every 1 degree F).
Sonic Booms
Sound producing objects send out sound waves in all directions. As it goes faster it is more difficult for waves to travel outward in front of it. When an airplane reaches a certain speed, air compresses of these sound waves and pile up into a dense area of compressed air.
Sonic booms that cause the least damage start at very high altitudes. By the time energy in the original area of compressed air is passed on to the ground, much of it has dissipated.
An explosion forms similar shock waves, except they move out equidistantly in all directions. Very rapid expansion of gases in an explosion compresses the surrounding air. As the shock wave of compressed air moves outward, it may flatten almost everything in its path until the pressure finally dissipates over a distance.
Sound reflection
Sound can be reflected, so we can direct or channel it in certain directions by using different devices.
Echoes
Because sound takes time to travel and can be reflected, it stands to reason that at certain distances you should be able to hear a distinctly separate reflection of an original sound called an echo.
The combination of a loud sound and many distant reflecting surfaces produces multiple echoes, or reverberations.
Sonar
SOund NAvigation and Ranging. It sends a sound wave through water and detects reflections from any direction. The time between an initial sound and its received echo enables a sonar operator to know the distance of a reflector.
Echolocation- the ability to use sound reflections.
(bats, dolphins and porpoises)
Absorbed Sounds
Porous acoustical tile on ceilings cut down sound reflections. A rough surface interferes with the wave reflection, just as light is diffused when it hits an irregular surface.
Reverberation and Reflected and Absorbed Sounds
Reverberation- multiple echo
After being produced, sound waves travel thorough the air in all directions. The various surfaces and materials absorb sound. The sound waves slowly lose a small amount of energy that is absorbed with each reflection until the waves gradually diminish and become inaudible.
Reverberation Time- the number of seconds that a sound’s average loudness can be heard, before it becomes completely inaudible under quiet conditions.
Rubber Bands and Pitch
The tightness, thickness, and length of a rubber band all affect its pitch. Sounds are higher with taut, thin, short strings; they are lower with looser, thicker, or longer strings on any stringed instrument.
Bottle Xylophone
Bottles made of plain glass make clearer, purer sounds than those made of rippled glass.
How pitch changes concepts
Many pilots of crop-dusting airplanes actually rely on sound to gauge the safeness of their air speed. Flying speed is therefore estimated by listening to the pitch of sound made by the vibration of the airplane’s struts and wires as the wind rushes past.
Stringed Instruments
Pitch depends on the length, tightness, and thickness of the strings. Shortening the strings causes faster vibrations, raising the pitch. Lengthening a string has the opposite effect. Tightening a string also increases pitch, whereas loosening a string decreases pitch. A think string vibrates more slowly than a thin one and so produces a lower-pitched sound.
Timbre – the quality of tone
Wind Instruments
A vibrating column of air makes the sound.
Pitch is regulated by changing the length of the air column vibrating within the instrument.
Homemade Instruments
An interesting way for children to learn about pitch and tonal quality is for them to make their own stringed and wind instruments.
Mass and Noise
When a noise is made, the amount of mass in the vibrating object usually determines the pitch.
The heavier the item the lower sound made
Hearing and Locating Sounds Concepts
In our hearing, the sound waves are channeled into the ear canal by the outer ear, whci acts as a megaphone in reverse. As sound waves collide with the ear drum, this thin membrane of stretched skin begins vibrating at the same frequency as the waves.
Inside the eardrum are three tiny, connected bones: the hammer, anvil, and stirrup. A vibrating eardrum starts the attached hammer shaking, and the movement is transmitted through the connected bones to the cochlea, or inner ear.
This snail shaped apparatus is filled with a watery fluid and lined with sensitive nerve endings that tail off to the auditory nerve and brain. The transmitted vibrations pass through the fluid and excite the nerve endings. These excitations are converted into electrical impulses that zip to the brain.
Hearing Ranges
Although are ears are sensitive to a wide range of pitches, there are limits to what we can hear. No one can detect a sound that vibrates less than about 16 times per second or more than 20,000 times per second. As we get older, the range is gradually narrowed.
Sounds that are inaudible to us are called infrasonic when they vibrate too slowly
Ultrasonic- when they vibrate to quickly
Locating Sounds
Most people can tell the direction which a sound comes, even when they are blindfolded.
Peters, Joseph M., Stout, David L. Science in Elementary Education Methods, Concepts, and Inquiries. Eleventh Edition. USA: 2011.
Meagan
Web Sources
Meagan Ricks - Background Information and Common Misconceptions - from web sources.
Common Misconceptions
Sounds can be produced without using any material objects.
Hitting an object harder changes the pitch of the sound produced.
Human voice sounds are produced by a large number of vocal cords that all produce different sounds.
Loudness and pitch of sounds are the same things.
You can see and hear a distinct event at the same moment.
Sounds can travel through empty space (a vacuum).
Sounds cannot travel through liquids and solids.
Sounds made by vehicles (like the whistle of a train) change as the vehicles move past the listener because something (like the train engineer) purposely changes the pitch of the sound.
In wind instruments, the instrument itself vibrates (not the internal air column).
Music is strictly an art form; it has nothing to do with science.
Sound waves are transverse waves (like water and light waves).
Matter moves along with water waves as the waves move through a body of water.
When waves interact with a solid surface, the waves are destroyed.
In actual telephones, sounds (rather than electrical impulses) are carried through the wires.
Ultrasounds are extremely loud sounds.
Megaphones create sounds.
Noise pollution is annoying, but it is essentially harmless.
Background Information
- Sound is a type of energy and is the result of vibrations (back and forth movement).
- The energy starts at a source and moves in waves which are called sound waves.
- Frequency is the "number of vibrations per second" and determines the pitch of a sound.
- "Pitch is how high or low a sound is."
- Higher frequencies result in higher pitch and lower frequencies result in lower pitch.
- A decibel is the measurement of how loud a sound is.
- A higher decibel sound is louder and a lower decibel sound is softer.
- "A decibel of 0 means no sound. Most people talk at 20 to 40 decibels. A sound greater than 120 decibels can hurt the inside part of your ears, resulting in reduced or total hearing loss."
- Listening to a tv or music too loudly and working around loud machinery can affect and decrease hearing.
Background Information and Clearing up Common Misconceptions- Physical Science Assessment Probe.
Recognize that sounds result from vibrations produced by an object or materials in contact with another object.
Sound is a form of energy caused by back-and-forth vibrations.
Amplitude is the size of the vibrations.
The loudness or softness of a sound depends on the amplitude.
Vibrations can also affect the pitch of a sound.
Pitch describes how high or how low a sound is that are produced by the vibrations.
Pitch is affected by changing the frequency of the vibrations, which is how quick or slow the object vibrates.
The more vibrations that occur per second the higher the frequency and pitch of the sound.
Early ideas about sound are connected to position and motion of objects.
At this grade the emphasis is on the objects, not on the air because this is hard for them to grasp, it is to abstract.
In this grade students learn about sound through musical instruments.
How fast things move will create different sound levels.
Children's explanations of how sound is produced can be sorted into three groups.
Physical properties of the sound producing materials.
The size of the force needed to produce the sound
Vibrations
Students do not have a general theory of sound being produced by vibration that can be transferred across different contexts.
Failure to recognize the role of vibration in sound may be linked to the failure to recognize the involvement of air as a medium in which vibrations are transferred.
All objects and materials that produce sound vibrate or cause surrounding objects or materials to vibrate.
AIMS Book
Jessica Forgety
Sound is a form of energy. Any form of energy can be changed from its form into another form of energy. Examples of energy are: light, heat, sound, electrical, mechanical, and chemical.
Sound travels. The speed at which it travels changes based on the present conditions. For example, during a lightning storm, sound travels at one mile per five seconds. That is fast!
Sound is produced by vibrations. A vibration is something that moves back and forth. In the case of sound, it is waves which are moved back and forth. “If you could see them, they would look like ripples that spread out when a pebble is dropped in a pond.”
Humans can hear vibrations at a certain range of speed per second, from 20 to 20,000 vibrations per second. Animals can hear sound that has higher vibration than 20,000 per second!
“The vibrating material may be a solid, liquid, or gas.” Typical sounds we hear are vibrations that travel through air. “Sound waves travel much faster through solids and liquids than through gases because the molecules of solids and liquids are closer together.”
“The pitch of the sound can be varied by changing the rate of vibration.” A pitch can be high or low. Pitch is based on the frequency of vibration.
Volume is the based on the amount of vibration traveling through a gas, solid, or liquid.
AIMS Education Foundation (2010). Energy Explorations: Sound, Light, and Heat. Fresno, California: Aims Education Foundation.
Text Book
Sound is produced by mechanical radiation, or the movement of energy from one place to another through a medium such as air or water (sound cannot be produced in a vacuum). Vibrations from an object moving back and forth cause molecules in the surrounding medium to begin vibrating and radiating waves of sound energy.
Sounds are vibrations and travel in waves.
Sound is produced by vibrating objects. The pitch of the sound can be varied by changing the rate of vibration.
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of chemicals. Energy is transferred in many ways.
Air is needed in all cases to make vocal cords vibrate. It is difficult to speak while breathing in because the normal way humans make sounds is by breathing out.
Molecules and sounds
Sounds are simply waves of compressed molecules pulsating outwards in all directions and planes from a vibrating source.
A sound fades away when energy behind the original vibrations is used in the transmitting process.
Loudness
Intensity or “loudness” is what we actually hear.
Loudness is a matter of individual perception.
Intensity can be consistently and accurately recorded by a sensitive sound detector in terms of decibel, a unit of measurement in sound. The distinction between loudness and intensity may be too subtle for most children.
A boost of energy forces any vibrating medium to vibrate to and fro more widely than usual, but in the same amount of time. It compresses molecules more forcefully, so the greater energy is able to move more molecules.
The farther away we are from the source, the weaker the sound that gets to us. Molecules are pushed less because progressively less energy is available.
Waves
Water is sometimes used as an analogy to teach how sound travels. A pebble is dropped into water, and a circular series of ripples spread out on the water’s surface. Useful to show class but contains two defects.
- Water waves are up and down motions that travel at right angles to the line of the waves, known as transverse waves. Sound waves come from back and forth motions that make longitudinal waves.
- Water waves move only horizontally, whereas sound waves travel outward in all planes.
The wave idea is useful to distinguish between sounds and noises. A sound consists of regularly pulsating vibrations; the time interval between each compression and rarefaction is the same. Noise is heard when irregular vibrations are passed on.Forced vibrations
Thomas Edison used his knowledge of forced vibrations when inventing the phonograph. He attached a sharp needle to a thin diaphragm that vibrated when sound waves struck it. The needle was placed against a cylinder wrapped with soft metal foil. As he spoke, he slowly cranked the cylinder around and around. The vibrating needles cut a series of impressions into the metal. To play back his sounds, he places the needle in the impression first scratched and cranked the cylinder. As it followed the impressions, the needle was forced to vibrate, thus causing the diaphragm to vibrate. Edison could hear his voice!
Sympathetic Vibrations
When tuning forks are of identical pitch, sound waves arrive at the proper time to set the still fork in motion. Each air compression pushes a prong as it starts to bend in from a previous one and each rarefaction arrives as the prong starts to bend back out. The steady, timed, push-pause-push rhythm sets the fork vibrating in almost the same way as you would push someone on a swing.
Natural Frequencies
Every solid object has a natural frequency of vibration.
Properties of Objects and Vibrations
Every object has certain physical properties that produce “appropriate” vibrations.
Strange sounds
Oven cooling racks, barbecue grills, and other grid like objects of metal make particularly strange, even eerie, sounds. These sounds come from the overtones produced when the many parts of the object vibrate differently.
Speeds of Sound
Light travels at about 297,000 kilometers (186,000 miles) per second. At sea level and 42 degrees F, sound waves move about 330 meters per second in the air, only as fast as a low-power rifle bullet. Sound also travels in liquids and solids.
It moves about 5 times faster in water than it does in air; in steel, sound may travel 15 times faster than it does in air.
Three conditions affect the speed of sound: density, the elasticity, or “springiness,” of the molecules conducting the sound, and temperature. Density by itself does not increase sound.
Sound and Temperature
Sound travels faster when temperature goes up. (1 ft per second fast in air for every 1 degree F).
Sonic Booms
Sound producing objects send out sound waves in all directions. As it goes faster it is more difficult for waves to travel outward in front of it. When an airplane reaches a certain speed, air compresses of these sound waves and pile up into a dense area of compressed air.
Sonic booms that cause the least damage start at very high altitudes. By the time energy in the original area of compressed air is passed on to the ground, much of it has dissipated.
An explosion forms similar shock waves, except they move out equidistantly in all directions. Very rapid expansion of gases in an explosion compresses the surrounding air. As the shock wave of compressed air moves outward, it may flatten almost everything in its path until the pressure finally dissipates over a distance.
Absorbing sound
Loosely woven, soft, fluffy materials absorb sounds well. Hard surfaces reflect sounds.
Sound reflection
Sound can be reflected, so we can direct or channel it in certain directions by using different devices.
Echoes
Because sound takes time to travel and can be reflected, it stands to reason that at certain distances you should be able to hear a distinctly separate reflection of an original sound called an echo.
The combination of a loud sound and many distant reflecting surfaces produces multiple echoes, or reverberations.
Sonar
SOund NAvigation and Ranging. It sends a sound wave through water and detects reflections from any direction. The time between an initial sound and its received echo enables a sonar operator to know the distance of a reflector.
Echolocation- the ability to use sound reflections.
(bats, dolphins and porpoises)
Absorbed Sounds
Porous acoustical tile on ceilings cut down sound reflections. A rough surface interferes with the wave reflection, just as light is diffused when it hits an irregular surface.
Reverberation and Reflected and Absorbed Sounds
Reverberation- multiple echo
After being produced, sound waves travel thorough the air in all directions. The various surfaces and materials absorb sound. The sound waves slowly lose a small amount of energy that is absorbed with each reflection until the waves gradually diminish and become inaudible.
Reverberation Time- the number of seconds that a sound’s average loudness can be heard, before it becomes completely inaudible under quiet conditions.
Rubber Bands and Pitch
The tightness, thickness, and length of a rubber band all affect its pitch. Sounds are higher with taut, thin, short strings; they are lower with looser, thicker, or longer strings on any stringed instrument.
Bottle Xylophone
Bottles made of plain glass make clearer, purer sounds than those made of rippled glass.
How pitch changes concepts
Many pilots of crop-dusting airplanes actually rely on sound to gauge the safeness of their air speed. Flying speed is therefore estimated by listening to the pitch of sound made by the vibration of the airplane’s struts and wires as the wind rushes past.
Stringed Instruments
Pitch depends on the length, tightness, and thickness of the strings. Shortening the strings causes faster vibrations, raising the pitch. Lengthening a string has the opposite effect. Tightening a string also increases pitch, whereas loosening a string decreases pitch. A think string vibrates more slowly than a thin one and so produces a lower-pitched sound.
Timbre – the quality of tone
Wind Instruments
A vibrating column of air makes the sound.
Pitch is regulated by changing the length of the air column vibrating within the instrument.
Homemade Instruments
An interesting way for children to learn about pitch and tonal quality is for them to make their own stringed and wind instruments.
Mass and Noise
When a noise is made, the amount of mass in the vibrating object usually determines the pitch.
The heavier the item the lower sound made
Hearing and Locating Sounds Concepts
In our hearing, the sound waves are channeled into the ear canal by the outer ear, whci acts as a megaphone in reverse. As sound waves collide with the ear drum, this thin membrane of stretched skin begins vibrating at the same frequency as the waves.
Inside the eardrum are three tiny, connected bones: the hammer, anvil, and stirrup. A vibrating eardrum starts the attached hammer shaking, and the movement is transmitted through the connected bones to the cochlea, or inner ear.
This snail shaped apparatus is filled with a watery fluid and lined with sensitive nerve endings that tail off to the auditory nerve and brain. The transmitted vibrations pass through the fluid and excite the nerve endings. These excitations are converted into electrical impulses that zip to the brain.
Hearing Ranges
Although are ears are sensitive to a wide range of pitches, there are limits to what we can hear. No one can detect a sound that vibrates less than about 16 times per second or more than 20,000 times per second. As we get older, the range is gradually narrowed.
Sounds that are inaudible to us are called infrasonic when they vibrate too slowly
Ultrasonic- when they vibrate to quickly
Locating Sounds
Most people can tell the direction which a sound comes, even when they are blindfolded.
Peters, Joseph M., Stout, David L. Science in Elementary Education Methods, Concepts, and Inquiries. Eleventh Edition. USA: 2011.
Web Sources
Common Misconceptions
Hapkiewicz, A. (1992). Finding a List of Science Misconceptions. MSTA Newsletter, 38 (Winter’92), pp. 11-14.
(found at: http://homepage.mac.com/vtalsma/misconcept.html#sound)
Background Information
- Sound is a type of energy and is the result of vibrations (back and forth movement).
- The energy starts at a source and moves in waves which are called sound waves.
- Frequency is the "number of vibrations per second" and determines the pitch of a sound.
- "Pitch is how high or low a sound is."
- Higher frequencies result in higher pitch and lower frequencies result in lower pitch.
- A decibel is the measurement of how loud a sound is.
- A higher decibel sound is louder and a lower decibel sound is softer.
- "A decibel of 0 means no sound. Most people talk at 20 to 40 decibels. A sound greater than 120 decibels can hurt the inside part of your ears, resulting in reduced or total hearing loss."
- Listening to a tv or music too loudly and working around loud machinery can affect and decrease hearing.
Vancleave, Janice. "Sound Facts." JVC's Science Fair Projects. May 23, 2010. October 17, 2011. http://scienceprojectideasforkids.com/2010/sound-facts/.